Extrusion involves the shaping of a work piece by forcing the work piece through an extrusion die using an extrusion press. During this process, the cross-sectional shape of the extruded work piece generally conforms to the shape of the extrusion die aperture. Metals and metal alloys can be extruded using either “hot extrusion” or “cold extrusion”, depending on the temperature at which the extrusion is carried out. During hot extrusion, the work piece and the extrusion die are both maintained at an elevated temperature. For example, aluminum and aluminum alloys are typically hot extruded at temperatures ranging from about 350 degrees Celsius (° C.) to about 500° C.
During the hot extrusion process, extrusion dies are typically pre-heated to the desired extrusion temperature in a separate oven prior to being installed in the extrusion press. This pre-heating of the extrusion dies reduces the time needed to bring the extrusion press to operating conditions, thereby increasing the throughput of the extrusion press.
Equipment for pre-heating extrusion dies has been previously considered. For example, U.S. Pat. No. 7,393,205 to Schwartz discloses a device for heating up extrusion dies prior to their installation in an extruder, whereby the extrusion dies are heated up to a prescribed temperature and kept at this temperature. The device comprises a gas-tight and thermally insulated oven housing that has at least one charging and discharging opening with an oven cover and, inside the oven housing, there is an impact nozzle field into which an extrusion die can be placed. The device is provided with a heating means that heats up a fluid that flows through the openings of the impact nozzle field.
U.S. Pat. No. 6,884,969 to Brach et al. discloses an infrared die oven having a die cradle for holding a die. A thermocouple is positioned within the die cradle to maintain it in direct contact with the die. A controller connected to the thermocouple continually reads the temperature of the die. When the die reaches a threshold temperature, the intensity of an infrared heating element in the oven is reduced. When the die reaches the desired temperature, the controller continuously adjusts the heater intensity to maintain the die at the desired temperature.
European Patent Application No. 0529198 to Perdersoli discloses a controlled-atmosphere furnace for preheating dies for extruding aluminum and alloys thereof. The furnace includes a supporting frame which delimits, at a portion of a side wall, at least one chamber which can be closed tight with respect to the outside environment, a chamber door which can be opened outward and has a supporting frame for a part to be preheated, and resistors for heating the chamber.
Automated handling equipment for extrusion dies has also been previously considered. For example, European Patent Application No. 0274366 to Zurru et al. discloses a die exchange device for horizontal axis extruding presses. The device comprises a supporting column provided with guides extending therealong, a carriage movable along the guides and provided with two rest shelves, each for a respective die holding slide, drive means to take each shelf to a die exchange position close to an extrusion working position of the press, and pusher means for shifting a die holding slide from the die exchange position to the extrusion working position, and vice versa.
Automated handling and pre-heating systems for polymer injection molding dies have also been previously considered. For example, U.S. Pat. No. 6,893,600 to Hughes et al. discloses a die preparation and exchange method, wherein dies to be inserted into an injection molding machine are electrically and fluidly heated prior to insertion so as to prepare the dies to make parts more quickly.
U.S. Pat. No. 4,518,338 to Hehl discloses a device for program-controllable exchange of injection molding dies and for continuous preconditioning of an injection molding die, prior to and during its insertion into the die closing unit of an injection molding machine. The device comprises a translation table with two die emplacements which are alternatingly movable into transverse alignment with the die clamping space, for transfer of a die assembly by means of an endless roller chain with drive pins and a drive rack entraining the die assembly. Each die emplacement has a captive drive rack which carries a coupling head for flexible temperature conditioning supply lines, and each die assembly has a matching coupling head with coupling valves and an identification code incorporated in a multi-conductor connection, all connections being established by the mere lowering of the die assembly onto its die emplacement.
Although known systems and methods for extrusion die pre-heating may be adequate, improvements are generally desired. It is therefore an object of the present invention to provide a novel die pre-heating system, apparatus and method.